HijackThis identifies O4 - HKLM\..\Run: [RIMBBLaunchAgent.exe] C:\Program Files\Common Files\Research In Motion\USB Drivers\RIMBBLaunchAgent.exe as a potential trojan noting "It seems that the name of this program is the same as the name of the file. In the most cases this is the result of trojans. To be sure, you should check this file."

How do I determine whether or not it is a trojan or otherwise undesirable?

I am assuming you got that information from some "HijackThis Analyzer"? The information is not correct - though most of what the analyzers provide is not to be considered as hard fact. Could you tell me which analyzer provided this incorrect information please?